Bernhard Lüscher | Eberly College of Science

We are working to improve our understanding of the role and function of GABAergic transmission in health and disease. GABA (gamma-aminobutyric acid) is the principal inhibitory neurotransmitter in the brain and known to exert most of its function by activation of so-called GABA(A) receptors. These receptors are GABA-gated chloride channels and they serve as the targets of several classes of clinically and therapeutically important psychoactive drugs, most notably the benzodiazepines (Valium, Xanax, Versed, etc). Based on knowledge derived from these drugs, GABA(A) receptors are known to modulate virtually every higher-order brain function (learning, memory, cognition, emotion, pain, motivation, muscle tension, etc).

A first line of research uses mouse genetics to model and investigate the molecular mechanisms underlying neuropsychiatric disorders. In particular, we are interested in the etiology of Major Depressive Disorder (MDD), a leading cause of total disability affecting about 17 percent of the human population at least once in their lives. Recent clinical evidence points to functional impairment of certain GABA-releasing interneurons and reduced brain concentrations of GABA as a likely cause of MDD. Using targeted mutagenesis in mice, we have shown that modest deficits in GABAergic transmission are sufficient to reproduce behavioral, cognitive, cellular, endocrine, and pharmacological alterations expected of a mouse model of depression. These mice, therefore, provide strong evidence that GABA deficits are not just an epiphenomenon of MDD, but that they can, in fact, be causal for MDD (reviewed in Luscher et al 2011, Mol. Psychiatry). Using these mice we have shown that defects in GABergic transmission can be causal for defects in the function of glutamate, the primary excitatory neurotransmitter in the brain, and that the defects in both GABA and glutamate can be reversed with the rapid-acting antidepressant, ketamine (Ren et al 2016)

In a second line of research, we are elucidating the mechanisms of antidepressant drug action. It is becoming increasingly clear that antidepressants act to ultimately increase and normalize GABAergic synaptic transmission even if they are designed to enhance the function of other neurotransmitters (serotonin, norepinephrine, glutamate, and their receptors. Therefore, we asked whether genetically enhancing the function of certain GABA-releasing interneurons would be sufficient to mimic the effects of above antidepressant drug treatments. We succeeded in showing that genetically increasing the excitability of GABA-producing interneurons known as somatostatin cells reproduced both biochemical and behavioral consequences of antidepressant drug treatment (Fuchs et al 2017).

Ongoing research seeks to better understand the molecular and cellular changes underlying MDD and antidepressant drug action, with the aim to design novel antidepressant drug treatments.